Author: Sonnad, K.G.
Paper Title Page
TUOAA01 3-Dimensional Modeling of Electron Clouds in Non-uniform Magnetic Fields 1059
  • S.A. Veitzer, P. Stoltz
    Tech-X, Boulder, Colorado, USA
  • J.A. Crittenden, K.G. Sonnad
    CLASSE, Ithaca, New York, USA
  Funding: This work was performed under the auspices of the Department of Energy as part of the ComPASS SCiDAC-2 project (DE-FC02-07ER41499) and by the National Science Foundation Grant PHY-0734867.
Electron clouds have the potential to pose serious limitations on accelerator performance in both hadron and lepton beams. Experiments using rf diagnostics are being performed to measure electron cloud densities at a number of accelerator facilities. However, it is difficult to calibrate plasma density with signal strength in these experiments, and modeling involves a number of technical and numerical challenges. Typically 2-Dimensional electrostatic methods have been used to model cloud buildup under beam crossing conditions. However, since traveling-wave rf experiments typically occur over many meters of beam pipe where magnetic fields are changing, one needs to develop 3-Dimensional electromagnetic models in order to accurately simulate rf diagnostics. We have developed accurate models of electron cloud-induced phase shifts in rf in a system with spatially varying magnetic field configurations using the plasma simulation code VORPAL. We present here results for measuring phase shifts in the CESR wiggler with realistic, spatially non-uniform magnetic field configurations.
slides icon Slides TUOAA01 [18.367 MB]  
WEYA02 Studies at CesrTA of Electron-Cloud-Induced Beam Dynamics for Future Damping Rings 2081
  • G. Dugan, M.G. Billing, K.R. Butler, J.A. Crittenden, M.J. Forster, D.L. Kreinick, R.E. Meller, M.A. Palmer, G. Ramirez, M.C. Rendina, N.T. Rider, K.G. Sonnad, H.A. Williams
    CLASSE, Ithaca, New York, USA
  • R.F. Campbell, R. Holtzapple, M. Randazzo
    CalPoly, San Luis Obispo, California, USA
  • J.Y. Chu
    CMU, Pittsburgh, Pennsylvania, USA
  • J.W. Flanagan, K. Ohmi
    KEK, Ibaraki, Japan
  • M.A. Furman, M. Venturini
    LBNL, Berkeley, California, USA
  • M.T.F. Pivi
    SLAC, Menlo Park, California, USA
  Funding: US National Science Foundation PHY-0734867, PHY-1002467, and PHY-1068662; US Dept. of Energy DE-FC02-08ER41538; and the Japan/US Cooperation Program.
Electron clouds can adversely affect the performance of accelerators, and are of particular concern for the design of future low emittance damping rings. Studies of the impact of electron clouds on the dynamics of bunch trains in CESR have been a major focus of the CESR Test Accelerator program. In this paper, we report measurements of coherent tune shifts, emittance growth, and coherent instabilities carried out using a variety of bunch currents, train configurations, beam energies, and transverse emittances, similar to the design values for the ILC damping rings. We also compare the measurements with simulations which model the effects of electron clouds on beam dynamics, to extract simulation model parameters and to quantify the validity of the simulation codes.
slides icon Slides WEYA02 [2.033 MB]  
WEPPR091 Multi-Particle Simulation Codes Implementation to Include Models of a Novel Single-bunch Feedback System and Intra-beam Scattering 3147
  • M.T.F. Pivi, A. Chao, C.H. Rivetta
    SLAC, Menlo Park, California, USA
  • F. Antoniou, K.S.B. Li, Y. Papaphilippou
    CERN, Geneva, Switzerland
  • M. Boscolo, T. Demma
    INFN/LNF, Frascati (Roma), Italy
  • K.G. Sonnad
    CLASSE, Ithaca, New York, USA
  Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP).
The beam tracking codes C-MAD and HEAD-TAIL have been enhanced to include a detailed model of a single-bunch feedback system. Such a system is under development to mitigate the electron cloud and the transverse mode coupling instability (TMCI) in the SPS and LHC at CERN. This paper presents the model of the feedback sub-systems: receiver, processing channel, filter, amplifier and kicker, which takes into account the frequency response, noise, mismatching and technological limits. With a realistic model of the hardware, it is possible to study the prototypes installed in the SPS and design a novel feedback system. The C-MAD code, which is parallel and optimized for speed, now also includes radiation damping and quantum excitation and a detailed model of Intra-Beam Scattering (IBS) based on the Zenkevich-Bolshakov algorithm, to investigate the IBS during damping and its effect on the beam distribution, especially the beam tails, that analytical methods cannot investigate. Intra-beam scattering is a limiting factor for ultra-low emittance rings such as CLIC and Super-B.
WEPPR087 Dependence of Beam Instabilities Caused by Electron Clouds at CesrTA Due to Variations in Chromaticity, Bunch Current and Train Length 3135
  • M.G. Billing, G. Dugan, M.J. Forster, D.L. Kreinick, R.E. Meller, M.A. Palmer, G. Ramirez, M.C. Rendina, N.T. Rider, J.P. Sikora, K.G. Sonnad, H.A. Williams
    CLASSE, Ithaca, New York, USA
  • J.Y. Chu
    CMU, Pittsburgh, Pennsylvania, USA
  • J.W. Flanagan
    KEK, Ibaraki, Japan
  • R. Holtzapple, M. Randazzo
    CalPoly, San Luis Obispo, California, USA
  Funding: Work supported by DOE Award DE-FC02-08ER41538, NSF Award PHY-0734867 and the Lepton Collider R&D Coop Agreement: NSF Award PHY-1002467.
Electron cloud-induced beam dynamics is being studied at CESRTA under various conditions. These measurements detect the the coherent self-excited spectrum for each bunch within a train and bunch-by-bunch beam size. In the position spectrum coherent betatron dipole and head-tail motion is detectable for each individual bunch within the train with a sensitivity for the motion of 1.1 (2) microns-rms in the vertical (horizontal) direction for a 1 mA bunch current. These techniques are utilized to study the electron cloud-related interactions, which cause the growth of coherent motion and beam size along the train. We report on the observations and results from studies of the instability growth vs. changes in chromaticity, the current per bunch and the length of the train.